content: /*
   * Copyright 2019 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.rxjava3.jdk8interop;
  
  import java.util.function.*;
  import java.util.stream.Collector;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.internal.disposables.*;
  import io.reactivex.rxjava3.internal.observers.DeferredScalarDisposable;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Collect elements of the upstream with the help of the Collector's callback functions.
   *
   * @param <T> the upstream value type
   * @param <A> the accumulated type
   * @param <R> the result type
   */
  final class ObservableCollector<T, A, R> extends Observable<R> {
  
      final ObservableSource<T> source;
  
      final Collector<T, A, R> collector;
  
      ObservableCollector(ObservableSource<T> source, Collector<T, A, R> collector) {
          this.source = source;
          this.collector = collector;
      }
  
      @Override
      protected void subscribeActual(Observer<? super R> s) {
          A initialValue;
          BiConsumer<A, T> accumulator;
          Function<A, R> finisher;
  
          try {
              initialValue = collector.supplier().get();
  
              accumulator = collector.accumulator();
  
              finisher = collector.finisher();
          } catch (Throwable ex) {
              Exceptions.throwIfFatal(ex);
              EmptyDisposable.error(ex, s);
              return;
          }
  
          source.subscribe(new CollectorObserver<>(s, initialValue, accumulator, finisher));
      }
  
      static final class CollectorObserver<T, A, R> extends DeferredScalarDisposable<R>
      implements Observer<T> {
  
          private static final long serialVersionUID = 2129956429647866524L;
  
          final BiConsumer<A, T> accumulator;
  
          final Function<A, R> finisher;
  
          A intermediate;
  
          Disposable upstream;
  
          boolean done;
  
          public CollectorObserver(Observer<? super R> actual,
                  A initialValue, BiConsumer<A, T> accumulator, Function<A, R> finisher) {
              super(actual);
              this.intermediate = initialValue;
              this.accumulator = accumulator;
              this.finisher = finisher;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
  
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T t) {
              if (!done) {
                  try {
                      accumulator.accept(intermediate, t);
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      upstream.dispose();
                      onError(ex);
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (done) {
                  RxJavaPlugins.onError(t);
              } else {
                  done = true;
                  intermediate = null;
                  downstream.onError(t);
              }
          }
  
          @Override
          public void onComplete() {
              if (!done) {
                  R r;
  
                  try {
                      r = finisher.apply(intermediate);
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      onError(ex);
                      return;
                  }
  
                  intermediate = null;
                  complete(r);
              }
          }
  
          @Override
          public void dispose() {
              super.dispose();
              upstream.dispose();
          }
      }
  }
  